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| United States Patent |
6,242,830
|
|
Katagiri
|
June 5, 2001
|
Motor
Abstract
In a motor having a bearing housing 7 with a hollow portion 23, a radial
bearing 9 held in the hollow portion 23, a thrust receiving plate 8
provided at one end of the hollow portion 23, and a rotary shaft 1 which
is rotatably supported by the radial bearing 9 in a state that an extreme
end thereof is in contact with the thrust receiving plate 8, the bearing
housing 7, shaped like a cup, includes a cylindrical portion 21 and a
bottom portion 22 defining one end of the cylindrical portion 21, the
cylindrical portion 21 and the bottom portion 22 define the hollow portion
23, the radial bearing 9 is firmly held with the inner surface of the
cylindrical portion 21, and the thrust receiving plate 8 is supported on
the bottom portion 22.
| Inventors:
|
Katagiri; Masayuki (Nagano, JP)
|
| Assignee:
|
Kabushiki Kaisha Sankyo Seiki Seisakusho (Nagaano, JP)
|
| Appl. No.:
|
414544 |
| Filed:
|
October 8, 1999 |
Foreign Application Priority Data
| Oct 09, 1998[JP] | 10-288292 |
| Current U.S. Class: |
310/90; 29/598; 384/114 |
| Intern'l Class: |
H02K 005/16 |
| Field of Search: |
310/90,89,44
384/113-115,279,428,902
29/598
|
References Cited
U.S. Patent Documents
| 5399025 | Mar., 1995 | Higuchi et al. | 384/428.
|
| 5466070 | Nov., 1995 | Nakasugi | 384/112.
|
| 5623382 | Apr., 1997 | Moritan et al. | 360/99.
|
| 5628569 | May., 1997 | Hayakawa et al. | 384/278.
|
| 5736799 | Apr., 1998 | Harano et al. | 310/90.
|
| 5762423 | Jun., 1998 | Mori et al. | 384/279.
|
| 5793561 | Aug., 1998 | Ibaraki et al. | 360/84.
|
| 5822846 | Oct., 1998 | Moritan et al. | 29/598.
|
| 5885005 | Mar., 1999 | Nakano et al. | 384/113.
|
| 6023114 | Feb., 2000 | Mori et al. | 310/90.
|
| Foreign Patent Documents |
| 8-331820 | Dec., 1996 | JP | .
|
Primary Examiner: Ramirez; Nestor
Assistant Examiner: Waks; Joseph
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas, PLLC
Claims
What is claimed is:
1. A motor comprising:
a cup-like bearing housing processed from a one piece metal material
including a cylindrical portion having a bearing fixing portion with an
inner circumferential surface and an outer circumferential surface and a
core holding portion with an inner circumferential surface and an outer
circumferential surface, a bottom portion, and a hollow portion defined by
said cylindrical portion and said bottom portion;
a radial bearing having an inner circumferential surface and an outer
circumferential surface held in said bearing fixing portion while the
outer circumferential surface of said radial bearing is in contact with
the inner circumferential surface of said bearing fixing portion;
a gap serving as an oil reservoir between the inner circumferential surface
of the core holding portion and the outer circumferential surface of said
radial bearing, said gap being disposed on an opposite side of the bearing
fixing portion from said bottom portion;
a stator core having an inner surface and an outer surface, the inner
surface of said stator core contacting the outer circumferential surface
of the core holding portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing; and
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate.
2. A motor in accordance with claim 1, wherein said bearing housing is
formed by shaping a metal sheet by a drawing process.
3. A motor in accordance with claim 1, wherein said cylindrical portion
further comprises:
a step portion between the bearing fixing portion and the core holding
portion, the core holding portion having a greater diameter than the
bearing fixing portion, said radial bearing made of a sintered
oil-impregnated alloy.
4. A motor in accordance with claim 1, wherein said bearing housing has a
stepped part, located between a bottom portion of said bearing fixing
portion and an end face of one end of said radial bearing, said rotary
shaft includes a reduced-diameter portion, which is located on an end of
said rotary shaft closer to said thrust receiving plate, and a ring-like
slipping-off preventing means placed between said stepped part of said
bearing housing and the end face of said radial bearing, while engaging
said reduced-diameter portion of said rotary shaft.
5. A motor in accordance with claim 1, wherein a flange-like portion, while
bent outward, is formed on an end of said bearing housing at which said
bearing housing is opened, and rotor slipping-off preventing means is
extended from a rotor of said motor toward said flange-like portion.
6. A motor in accordance with claim 1, wherein axially elongated grooves
are formed in the outer circumferential surface of said radial bearing or
the inner circumferential surface of said bearing housing, said grooves
communicating a space, which is formed by an end face of one end of said
radial bearing and said bottom portion of said cup-like bearing housing,
with another space located closer to an open end of said cup-like bearing
housing.
7. A motor in accordance with claim 1, wherein said motor includes a stator
plate, said stator plate includes burring portions being arranged in a
ring-like fashion, and said burring portions hold the outer
circumferential surface of said bearing housing.
8. A motor in accordance with claim 7, wherein said burring portions of
said stator plate hold said bearing housing such that said bearing housing
is movable in axial or circumferential directions.
9. A motor in accordance with claim 8, wherein said bearing housing is
fixedly coupled to said stator plate in a state that said bearing housing
is set at a predetermined position of said burring portions and held by
said burring portions.
10. A motor in accordance with claim 7, where core fixing portions are
formed by bending a part of said stator plate in the vicinity of said
burring portion, and a stator core is brought into contact with said core
fixing portions.
11. A motor comprising:
a rotor portion with a rotary shaft;
a stator portion disposed facing said rotor portion;
a cup-like bearing housing provided from a one piece metal material and
integrally including a cylindrical portion and a bottom portion, the
cylindrical portion having a bearing fixing portion;
a radial bearing, held by said bearing fixing portion, rotatably supporting
said rotary shaft in a radial directions while being held within said
bearing housing, a gap serving as an oil reservoir and being defined by
the cylindrical portion and an outer circumferential surface of the radial
bearing at a portion opposite to the bottom portion relative to the
bearing fixing portion, where a outer circumferential surface of a core
holding portion of said bearing housing holds an inner circumference of a
core of said stator portion; and
a thrust bearing, disposed on said bottom portion, for supporting said
rotary shaft in a thrust direction.
12. A motor in accordance with claim 11, wherein said radial bearing is a
sintered oil-impregnated bearing, and said bearing housing includes a
bearing fixing portion for holding said radial bearing having been press
fit thereinto, a positioning portion for positioning said radial bearing
within said bearing housing, and oil storing portion for storing oil to be
impregnated into aid sintered oil-impregnated bearing.
13. A motor in accordance with claim 12, wherein a disc hub for the
attaching and detaching of a disc is attached to said rotary shaft, and
the directions of attaching and detaching the disc are coincident with the
contacting direction of said thrust bearing.
14. A motor comprising:
a cup-like bearing housing integrally including a cylindrical portion, a
bottom portion and a hollow portion defined by said cylindrical portion
and said bottom;
a radial bearing held in said hollow portion while being in contact with an
inner surface of said cylindrical portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing; and
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate;
wherein said bearing housing has a stepped part, which is located between
said bottom portion thereof and an end face of one end of said radial
bearing, said rotary shaft includes a reduced-diameter portion, which is
located on an end of said rotary shaft closer to said thrust receiving
plate and ring-like slipping-off preventing means is placed between said
stepped part of said radial bearing and the end face of said radial
bearing, while engaging said reduced-diameter portion of said rotary
shaft.
15. A motor comprising:
a cup-like bearing housing integrally including a cylindrical portion, a
bottom portion and a hollow portion defined by said cylindrical portion
and said bottom;
a radial bearing held in said hollow portion while being in contact with an
inner surface of said cylindrical portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing; and
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate;
wherein a flange-like portion, while bent outward, is formed on an end of
said bearing housing at which said bearing housing is opened, and rotor
slipping-off preventing means is extended from a rotor of said motor
toward said flange-like portion.
16. A motor comprising:
a cup-like bearing housing integrally including a cylindrical portion, a
bottom portion and a hollow portion defined by said cylindrical portion
and said bottom;
a radial bearing held in said hollow portion while being in contact with an
inner surface of said cylindrical portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing;
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate;
wherein said motor includes a stator plate, said stator plate includes
burring portions being arranged in a ring-like fashion, and said burring
portions hold an outer surface of said bearing housing.
17. A motor comprising:
a cup-like bearing housing integrally including a cylindrical portion, a
bottom portion and a hollow portion defined by said cylindrical portion
and said bottom;
a radial bearing held in said hollow portion while being in contact with an
inner surface of said cylindrical portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing;
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate;
wherein said burring portions of said stator plate hold said bearing
housing such that said bearing housing is movable in axial or
circumferential directions.
18. A motor comprising:
a cup-like bearing housing integrally including a cylindrical portion, a
bottom portion and a hollow portion defined by said cylindrical portion
and said bottom;
a radial bearing held in said hollow portion while being in contact with an
inner surface of said cylindrical portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing;
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate;
wherein said bearing housing is fixedly coupled to said stator plate in a
state that said bearing housing is set at a predetermined position of said
burring portions and held by said burring portions.
19. A motor comprising:
a cup-like bearing housing integrally including a cylindrical portion, a
bottom portion and a hollow portion defined by said cylindrical portion
and said bottom;
a radial bearing held in said hollow portion while being in contact with an
inner surface of said cylindrical portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing;
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate;
where core fixing portions are formed by bending a part of said stator
plate in the vicinity of said burring portion, and a stator core is
brought into contact with said core fixing portions.
Description
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a motor well adaptable for a CD-ROM
driver, a DVD-ROM drive or others.
2. Related art
A brushless motor, disclosed in JP-A-8-331820, has been known for a motor
used for the CD-ROM drive, for example. The brushless motor follows. A
rotary shaft is supported with aid of a radial bearing as a sintered
oil-impregnated bearing and a thrust plate within a cylindrical bearing
housing. The radial bearing is located in the upper portion of the bearing
housing. The inside diameter of the lower part of the bearing housing is
larger than that of the upper part thereof. A dish-like thrust cap is
mounted on the lower part of the bearing housing. A thrust plate is
disposed between the lower end of the rotary shaft and the thrust cap.
The motor is capable of preventing bearing lubricating oil from flowing out
of a thrust receiving portion since the dish-like thrust cap is mounted on
the lower part of the bearing housing, and a thrust plate is disposed
between the lower end of the rotary shaft and the thrust cap. In the
radial bearing fixed to the bearing housing, the lubricating oil receives
a pumping action with rotation of the shaft, and flows downwardly of the
inner wall of the bearing housing. The oil thus flowing out reaches a
portion where the thrust cap is attached to the bearing housing. Even if
the thrust cap is attached in press fitting manner, a minute gap will
possibly be formed between the cap and the housing since those members are
separate members. If such a gap is present, oil will leak through the gap
outside the thrust cap.
When a disc is attached to the disc hub integral with the rotary shaft, a
force is applied to the fixing portion for the thrust cap and the bearing
housing in a direction in which the thrust cap is pulled out. As a result,
the oil is likely to flow outside from the fixing portion.
SUMMARY OF INVENTION
Accordingly, an object of the present invention is to provide a motor which
is free from the flowing of bearing lubricant oil outside the bearing
housing, and has a long lifetime and a high reliability.
An aspect of the present invention, there is provided a motor comprising:
a cup-like bearing housing integrally including a cylindrical portion, a
bottom portion and a hollow portion defined by said cylindrical portion
and said bottom;
a radial bearing held in said hollow portion while being in contact with
the inner surface of said cylindrical portion;
a thrust receiving plate disposed at said bottom portion of said cup-like
bearing housing; and
a rotary shaft rotatably supported by said radial bearing in a state that
an extreme end thereof is in contact with said thrust receiving plate.
In the present invention, the bearing housing, which is shaped like a cup,
includes a cylindrical portion and a bottom portion closing one end of the
cylindrical portion. Therefore, in the resultant motor, no bearing oil
flows outside from the bottom portion of the bearing housing.
Shaping a metal sheet by drawing process forms the bearing housing.
Therefore, the number of parts required is reduced. The unit form of the
bearing housing eliminates the leakage of bearing oil out of the housing.
A gap, which may be utilized for an oil reservoir, is formed between the
inner surface of the cylindrical portion of the bearing housing and the
outer surface of the radial bearing. Provision of the gap prevents the
bearing oil from leaking out of the bearing housing, elongates a lifetime
of the motor, and allows bearing oil replenishment at the time of
assembling the rotor into the structure.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cross sectional view showing a portion of a motor which
constitutes a first embodiment of the present invention.
FIG. 2 is a cross sectional view showing a portion of another motor which
constitutes a second embodiment of the present invention.
FIG. 3(a) and FIG. 3(b) are cross sectional views showing a bearing housing
which may be used for the motor of the invention.
FIG. 4 is a perspective view showing a burring portion which may be used
for the motor of the invention.
FIG. 5 is a cross sectional view showing a way of assembling a bearing
assembly, which maybe used for the motor of the invention.
FIG. 6 is a cross sectional view showing a thrust bearing assembly which
may used for the motor of the invention.
FIG. 7(a)-FIG. 7(c) are side views showing a way of assembling a stator
assembly which may be used for the motor of the invention.
FIG. 8 is a side view showing a way of assembling a rotor assembly which
may be used for the motor of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The preferred embodiments of the present invention will be described with
reference to the accompanying drawings. As shown in FIG. 1, a bearing
housing 7 includes a cylindrical portion 21, a bottom portion 22 and a
hollow portion 23. To form the bearing housing 7, a metal sheet is pressed
into a cup-like shape having the cylindrical portion 21 and the bottom
portion 22 closing one end of the cylindrical portion 21. A thrust
receiving plate 8 is placed on the bottom portion 22 within the hollow
portion 23 of the bearing housing 7 while being centered. A radial bearing
9 is disposed within the cylindrical portion 21 of the bearing housing 7
while being in contact with the inner surface (peripheral) of the
cylindrical portion 21. A rotary shaft 1 is supported by the inner surface
of the radial bearing 9 in a state that it is rotatable about its center
axis. In this case, the rotary shaft 1 rotates in a state that a extreme
end 24 of the rotary shaft 1 is in contact with the thrust receiving plate
8. In the present embodiment, the drawing process is used for shaping a
metal sheet into the cup-like bearing housing 7 with the bottom portion
22. However, any other suitable process may be used for the same purpose,
as a matter of course.
A hub 2 to which a disc is set is secured onto the upper end of the rotary
shaft 1. A rotor case 3 is fastened to the under surface of the hub 2. A
rotor magnet 4, cylindrically shaped, is fastened onto the inner surface
of the rotor case 3. A stator core 5 is fit to the outer surface
(peripheral) of the cylindrical portion 21 of the bearing housing 7, while
being disposed facing the inner surface of the rotor magnet 4. The stator
core 5 includes a plural number of protruding poles, which are radially
extended and equiangularly disposed around the core. Each protruding pole
has a drive coil 15 wound thereon. The rotor case 3, the hub 2 and the
rotary shaft 1 are rotatable in unison.
The bearing housing 7 has a stepped part 26, which is located between its
bottom portion 22 and an end face 28 of one end of the radial bearing 9.
The inside diameter of an upper portion of the cylindrical portion 21
above the stepped part 26 is larger than that of a lower portion of the
cylindrical portion below the stepped part 26. The rotary shaft 1 includes
a reduced-diameter portion 27, located between an extreme end 24 thereof
closer to the thrust receiving plate 8 and an end face 28 of one end of
the radial bearing 9. A washer 10 as ring-like slipping-off preventing
means is placed between the stepped part 26 of the radial bearing 9 and
the end face 28 of the radial bearing 9. The washer 10 engages the
reduced-diameter portion 27 of the rotary shaft 1. Bringing the washer 10
into contact with the end face 28 of the radial bearing 9 reliably
prevents the rotary shaft 1 from slipping off.
An upper portion of the bearing housing 7 above the stepped part 26 forms a
bearing-fixing portion 32 the inside diameter of which is somewhat shorter
than the outside diameter of the radial bearing 9. The radial bearing 9 is
tightly inserted into the bearing-fixing portion 32 of the bearing housing
7. With this, The radial bearing 9 is fixedly supported with the
bearing-fixing portion 32.
Another stepped part 34 is formed at a mid-position of the cylindrical
portion 21 of the bearing housing 7. With provision of the stepped part
34, approximately the half of the axial length of the radial bearing 9 is
held with the bearing fixing portion 32 of the bearing housing 7, which
extends below the stepped part 34. A gap 33 is formed between the inner
surface of the cylindrical portion 21 of the bearing housing 7 and the
outer surface of the radial bearing 9. The gap 33 may be formed by
selecting the inside diameter of the cylindrical portion 21 located above
the stepped part 34 to be larger that outside diameter of the radial
bearing 9. In an alternative formation of the gap 33, the outside diameter
of the upper portion of the radial bearing 9 is selected to be larger than
the inside diameter of the cylindrical portion 21 without forming the
stepped part 34 on the cylindrical portion 21 of the bearing housing 7. A
radial distance of the gap 33 is selected to be at least 25 .mu.m, for
example.
The gap 33 is utilized for an oil reservoir. When the rotary shaft 1 is
rotated, oil is emitted from the radial bearing 9. The oil raises from the
upper end face 35 of the radial bearing 9; flows to the outer periphery
side of the radial bearing 9; stays in the rotor case 3; and returns to
the radial bearing 9. It is noted here that the oil does not leak out of
the bearing housing 7. This fact ensures a reliability and long lifetime
of the resultant motor.
As shown in FIG. 4, a base plate 6 includes burring portions 39 formed by
burring and core fixing portions 38 formed by bending a part of the base
plate 6 in the vicinity of the burring portion 39. The core fixing
portions 38 are angularly disposed at angular intervals each of
120.degree. while being located each between the two adjacent the burring
portions 39 being arranged in a ring-like fashion. Each core fixing
portions 38 is shaped to include a vertical portion located outside the
related burring portions 39 and a horizontal portion horizontally
extending from the vertical portion toward a space between the related
adjacent burring portions 39. The bearing housing 7 is press fit into the
arrangement of the burring portions 39; the outer surface of the
cylindrical portion 21 of the bearing housing 7 is firmly held with the
inner surfaces of the burring portions 39. Accordingly, a verticality of
the bearing housing 7 with respect to the base plate 6 is secured by the
arrangement of the burring portions 39. To this end, a length of the inner
surface 41 of each of the thus arranged burring portions 39 is selected so
as to secure the verticality of the bearing housing 7 with respect to the
base plate 6. An upper surface 55 (as a disc placing surface) of the hub 2
may be adjusted since an axial position of the bearing housing 7, viz., a
press-fitting height, of the burring portions 39 may be adjusted with
respect to the inner surfaces 41 of the burring portions 39. The
verticality of the bearing housing 7 with respect to the arrangement of
the burring portions 39 is adjusted as intended and then in this state
those are coupled together by welding or bonding.
The embodiment provides a stator core fixing structure with a high rigidity
for the following reason. The upper surfaces 42 of the fixing portions 38
are brought into contact with the lower surface of the stator core 5; the
height of the stator core 5 is adjusted; and the cylindrical portion 21 of
the bearing housing 7 holds the inner surface of the stator core 5 in a
compressive manner.
FIG. 5 is a cross sectional view useful in explaining a way of assembling a
bearing assembly. As shown, a jig 51 is disposed to guide the rotary shaft
1 for its centering, and the radial bearing 9 is inserted into the jig 51.
A guide bar 52 is inserted into the radial bearing 9. The thrust receiving
plate 8 is put on the top of the guide bar 52; the washer 10 is placed
between the thrust receiving plate 8 and the end face 28 of one end of the
radial bearing 9; and in this state, the bearing housing 7 shaped like a
cup is press fit to the thus assembled structure. In this case, the
bearing housing 7 is moved till its bottom portion 22 comes into contact
with the thrust receiving plate 8. In this state, the outer surface of the
radial bearing 9 is firmly fixed with the bearing-fixing portion 32 of the
bearing housing 7. In actually assembling the rotor, the guide bar 52 is
pulled out of the radial bearing 9 and the rotary shaft 1 is inserted into
the same instead.
FIG. 3 is a cross sectional view of the bearing housing 7, taken line a--a
in FIG. 5. Axially elongated grooves 31 are formed in the inner surface of
the bearing housing 7. The grooves 31 communicates a space 29, which is
formed by the end face 28 of one end of the radial bearing 9 and the
bottom portion 22 of the bearing housing 7, with a space 30 located closer
to the opening end of the bearing housing 7. FIG. 30A shows a cross
sectional view of the bearing housing 7 in which three axially elongated
grooves 31a semicircular in cross section are formed in the inner surface
of the bearing fixing portion 32 while being equiangularly arranged. FIG.
3B shows a cross sectional view of the bearing housing 7 in which three
axially elongated grooves 31b shaped like U in cross section are formed in
the inner surface of the bearing fixing portion 32 while being
equiangularly arranged.
Another bearing housing 7 is shown in FIG. 6. The bearing housing 7
includes three axially elongated grooves 31c, which are formed in the
outer surface of the radial bearing 9 while being arranged equiangularly.
As recalled, in each of the above two bearing housings 7, the grooves
axial grooves 31a (31b) are formed in the inner surface of the bearing
housing 7. The size and the number of grooves may properly be selected in
accordance with a kind of motor used.
Thus, at least one groove 31 is formed in the inner surface of the bearing
housing 7 or the outer surface of the radial bearing 9. The groove 31
yields the following advantages. When the rotary shaft 1 is inserted into
the radial bearing 9, air present in the space 29 in the vicinity of the
bottom portion 22 of the bearing housing 7 is guided outside. Further,
provision of the groove 31 prevents oil from overflowing through the edge
of the radial bearing 9 when the rotary shaft 1 is inserted into the
radial bearing 9.
A fixing strength of the outer surface of the radial bearing 9 may be
adjusted to a necessary one in a manner that a balance between the outer
surface of the radial bearing 9 with the bearing fixing portion 32 of the
bearing housing 7 when those are in contact with each other is varied by
varying the combination of the number and the size of the of the grooves
31 as oil-leak preventing means and the axial length of the bearing fixing
portion 32 of the bearing housing 7.
Further, with provision of the grooves 31 formed in the bearing-fixing
portion 32 of the bearing housing 7 or in the outer surface of the radial
bearing 9, part of oil moves to the washer 10 and the extreme end of the
radial bearing 9. The oil present there functions to stabilize a
frictional resistance between the thrust receiving plate 8 and the rotary
shaft 1 for a long time.
FIG. 7 is a side view showing a way of assembling a stator assembly, which
may be used for the motor of the invention. A bearing assembly formed by
inserting the radial bearing 9 into the bearing housing 7, as shown in
FIG. 7A, is forcibly inserted into the center hole of the stator core 5 in
a state that the opening end of the assembly is directed upward. As a
result, a close contact is established between the outer surface of the
bearing housing 7 and the inner surface of the center hole of the stator
core 5, and the former is fixed by the latter. As already stated, the base
plate 6 includes the burring portions 39 formed by burring and the core
fixing portions 38 formed by bending a part of the base plate 6 at a
location near the burring portion 39. After forcibly inserted and fixed by
the stator core 5, the bearing assembly is press fit into the hole defined
by the burring portions 39 (FIG. 7B). Then, the outer (peripheral) surface
of the cylindrical portion 21 of the bearing housing 7 is firmly held by
the inner surfaces 41 of the burring portions 39, and the lower surface 53
of the stator core 5 is put on the upper surfaces 42 of the core fixing
portions 38, and positioned thereat (FIG. 7C). Incidentally, bearing oil
may be put, for its replenishment, into the gap 33 located between the
radial bearing 9 and the bearing housing 7 after the stator assembly is
assembled.
A height H from the upper surface 54 (as a reference surface) of the base
plate 6 to the disc placing surface 55 of the hub 2 is given by
H=A-B (1)
where A is a distance from the extreme end 24 of the rotary shaft 1 which
is located closer to the thrust receiving plate 8 to the disc placing
surface 55, and B is a distance from the reference surface 54 to the upper
surface of the thrust receiving plate 8 (FIGS. 1, 5, 7C and 8). The length
of the rotary shaft 1, as shown in FIG. 8 determines the distance A. The
distance B varies with a position of the bearing housing 7 when it is
press fit into the burring portions 39 of the base plate 6 (FIG. 7C).
(This position of the bearing housing 7 will be referred to a "fitting
position".) From this, it is seen that the height H ranging from the
reference surface 54 to the disc placing surface 55 may be adjusted by the
"fitting position" of the bearing housing 7. It is noted here that the
burring portions 39 holds the bearing housing 7 so as to allow the bearing
housing 7 to be movable in the axial and circumferential directions.
Therefore, adjusting the fitting position in an actual assembling work can
precisely set the height H.
As well known, to operate the thus constructed motor, electric current is
fed to the drive coils in accordance with angular positions of the rotor
magnet 4. Electromagnetic forces are developed between the stator core 5
and the rotor magnet 4. The rotor magnet 4, and the rotor case 3 and the
hub 2, which are coupled together with the rotor magnet 4, are driven to
rotate in unison.
The FIG. 1 motor described above includes the washer 10 as means for
preventing the rotary shaft 1 from slipping off. Another rotor
slipping-off means may be used as shown in FIG. 2. In a structure of the
motor shown in FIG. 2, the rotor slipping-off preventing means 10 (FIG. 1)
is not used; the bearing housing 7 does not include the stepped part 26;
and the rotary shaft 1 does not include the reduced-diameter portion 27.
Also in the FIG. 2 structure, a centering guide portion 40, while being
protruded, is formed on the end face of the lower end of the radial
bearing 9. The centering guide portion 40 is used for centering the thrust
receiving plate 8.
As shown, a flange-like portion 36 is formed on the end of the bearing
housing 7 at which the housing is opened. Rotor slipping-off preventing
means 37 is extended from a horizontal part 3a of the rotor case 3, which
is mounted on the under side of the hub 2, toward the flange-like portion
36. In a normal state of the motor, the upper surface 37a of the rotor
slipping-off preventing means 37 is separated from the lower surface 36a
of the flange-like portion 36. When impact is imparted on the motor, the
lower surface 36a of the flange-like portion 36 is brought into contact
with the upper surface 37a of the rotor slipping-off preventing means 37,
thereby preventing the rotor from slipping off.
The motor of FIG. 2 has the following advantages because of its technical
feature not using the rotor slipping-off preventing means. If the radial
bearing of the FIG. 2 motor has the axial length equal to that of the
radial bearing of the FIG. 1 motor, the radial bearing 9 which is placed
within the bearing housing 7 may be low in height. This leads to the
thinned motor structure. Further, the upper end face 35 of the radial
bearing 9 may be located below the flange-like portion 36 of the bearing
housing 7. This feature provides a structure making it difficult for oil
to flow out of the bearing housing 7.
In the present invention, the drawing process is used for shaping a metal
sheet into the cup-like bearing housing with the bottom portion in order
to firmly hold the radial bearing 9 and the stator core 5 with the bearing
housing. Use of the cup shape of the bearing housing 7 eliminates the
leakage of oil that is contained in the radial bearing 9 from its bottom
portion. The resultant motor is high in reliability and long in lifetime.
The gap 33 provided between the radial bearing 9 and the bearing housing 7
functions to prevent oil from leaking, and further may be used as a space
for the replenishing of bearing oil at the time of assembling the rotor
into the structure.
While the present invention has been described using specific embodiments,
it should be understood that the invention may variously be modified,
changed and altered within the true spirits of the invention.
In the present invention, the bearing housing, which is shaped like a cup,
includes a cylindrical portion and a bottom portion closing one end of the
cylindrical portion. Therefore, in the resultant motor, no bearing oil
flows outside from the bottom portion of the bearing housing.
Shaping a metal sheet by drawing process forms the bearing housing.
Therefore, the number of parts required is reduced. The unit form of the
bearing housing eliminates the leakage of bearing oil out of the housing.
A gap, which may be utilized for an oil reservoir, is formed between the
inner surface of the cylindrical portion of the bearing housing and the
outer surface of the radial bearing. Provision of the gap prevents the
bearing oil from leaking out of the bearing housing, elongates a lifetime
of the motor, and allows bearing oil replenishment at the time of
assembling the rotor into the structure.
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